Fluid distribution system



Dec. 22, 1964 c. w. KOONS 3,162,095

FLUID DISTRIBUTION SYSTEM Filed March 26, 1962 INVENTOR CharLesW. Koons BY JJA ATTORNEYS United States Patent 3,162,095 FLUID DISTUTION SYSTEM Charles W. Koons, Kalamazoo, Mich assignor to The .lfew York Air Brake Company, a corporation of New ersey Filed Mar. 26, 1962, Ser. No. 182,425 3 Claims. (Cl. 91414) This invention relates to fluid distribution systems in which the output of a source of pressure fluid is selectively delivered to a plurality of fluid demands. A typical system of this kind is the hydraulic circuit frequently used to position the material handling bucket of a loader. This circuit includes a pump and reservoir, a pair of directional control valves, and a pair of doubleacting piston motors, one of the motors, called the lift motor, being arranged to raise and lower the bucket, and the other motor being arranged to tilt the bucket. For any given installation, there is an infinite number of combinations of pressure and efiective motor area that can be used to handle the design load. Motor area, and consequently, motor size, varies in inverse relation to system pressure and, therefore, space and weight can be conserved by using high pressures. However, since high pressure systems require stronger materials, better fittings and seals, and increase maintenance problems, the selection of a satisfactory combination of pressure and motor area must involve a compromise. In plural motor systems, it sometimes happens that the factors influencing the selection of pressure-area combinations for the various motors are not the same, and that the optimum circuit design cannot be realized by operating all of the motors at the same pressure.

The object of this invention is to provide a fluid distribution system in which the fluid furnished by the supply pump can be delivered at one pressure to one or several motors and at a different pressure to the remaining motors. According to the invention, the system includes a dual setting relief valve whose cracking pressure is changed automatically by operation of one or more of the control valves. This arrangement allows. the circuit designer more freedom in making the design compromise for each demand and thus results in more nearly optimum circuit designs.

The preferred form of the invention will be described in detail with reference to the accompanying drawing whose single figure is a schematic diagram of a typical hydraulic circuit incorporating the invention.

As shown in the drawing, the circuit comprises a multi-plunger directional control valve 11 having inlet and exhaust ports 12 and 13, respectively, a positive displacement pump 14, a sump 15, and a pair of double-acting differential area piston motors 41 and 44. The directional control valve 11 is of the series-parallel open center type and includes a housing containing two through bores 16 and 17 which receive the three-position reciprocable valve plungers 18 and 19, respectively. The bore 16 is encircled by seven longitudinally spaced annular chambers 21-24 and 21'23', while the bore 17 is encircled by seven longitudinally spaced annular chambers 3134 and and 3133'. The chambers 21, 21, 31, 31', and 34 are in continuous communication with the sump 15 through exhaust manifold 29 and exhaust port 13. When the valve plunger 29 is in the illustrated neutral position, chamber 24 is also connected with the sump 15 through the parallel passages 27 and 2S, annular chambers 33 and 33, manifold 29, and the exhaust port 13. The chambers 23 and 23' are directly connected with the pump 14 through the inlet port 12 and the parallel supply passages 25 and 26. When the valve plungen18 is in a neutral position (the position shown in the drawing), the chambers 33 and 33 are connected with the pump 14 through the inlet 3,162,095 Patented Dec. 22, 1964 port 12, the parallel passages 25, 26 the chamber 24 and the parallel passages 27, 28. Chambers 22 and 22' are connected with the opposite sides of motor 41 through conduits 42 and 43, and chambers 32 and 32 are connected with the opposite sides of motor 44 through conduits 45 and 46.

The valve plungers 18 and 19 are of conventional design as shown by reference to Patent No. 2,362,944, issued November 14, 1944. Valve plunger 18 is formed with a first set of radial ports 35 and 36 that are interconnected by a closed axial bore, a second set of radial ports 35 and 36' that are interconnected by a second closed axial bore, two grooves 47 and 48, and three lands 37, 38 and 39. The valve plunger 19 is identical to the plunger 18 so corresponding parts are indicated by the same numerals with the postscript a added for clarity. I

A conventional pilot-operated pressure relief valve 51 is provided for limiting the pressure that pump 14 supplies to the motors. The relief valve comprises a seat 68 and a spherical head 67 that is pressed into the reciprocable plunger 66. To the right of the plunger 66 is a control chamber 63 that is in restricted communication with inlet 12 through restricted passage 64. Spring 65 and the fluid pressure in chamber 63 bias the plunger 66 and head 67 to the left, and, therefore, during normal operation of the control system, head 67 is in sealing engagement with its seat 68. Passage 69 connects chamber 63 with the sump 15 through exhaust manifold 29, and this passage is normally closed by the pilot valve 52- which is biased to a closed position by the Spring 53. Spring 53 is seated on plug 54 which is screwed into reciprocable seat 55. Movement of seat 55 within chamber 56 is limited by shoulder 57 and the inner end of fitting 59. There is a. radial clearance 58 between the outside diameter of seat 55 and the inside diameter of chamber 56 which defines a restricted vent path connecting the space in chamber 56 to the right of seat 55 with exhaust manifold 29. The fitting 59, fastened to the housing 11, is connected with a conduit 61 which extends be tween the right side of chamber 56 and a port 62 in the bore 16. Port 62 is so positioned that it is closed by land 37 when plunger 18 is in either its neutral or right-hand position and is connected with annular chamber 23 by groove 47 when plunger 18 is in its left-hand position.

Operation The valve plunger 18 is movable either to the left or right from its neutral position and such movement control the operation of motor 41. It is apparent that when the plunger 18 is in its extreme left hand position, the head end of motor 41 is connected with the pump 14 via inlet port 12, passage 26, chamber 23', ports 36 and 35', motor chamber 22' and conduit 43, and the rod end of motor 41 is connected with the sump 15 via conduit 42, motor chamber 22, ports 36 and 35, chamber 21, manifold 29, and exhaust port 13. When the valve plunger 18 is in the extreme right-hand position, the rod end of motor 41 is connected with the pump 14 by way of inlet port 12, passage 25, chamber 23, ports 36 and 35, motor chamber 22 and conduit 42, and the head end of the motor is connected with the sump 15 by way of conduit 43, ports 36 and 35', chamber 21', manifold 29 and exhaust port 13. For a more detailed description of how such a valve controls a fluid motor, see the above mentioned patent.

Functioning in the same manner as plunger 18, plunger 19 controls the operation of motor 44. Of course, since the plungers 18 and 19 are in'a series supply path, movement of plunger 18 causes land 38 and either land 37 or 39 to interrupt flow from pump 14 to chambers 33 and 33'. v

' Whenever plunger 18. is placed in its extremeleft-hand position (i.e., the position in which pump 14 is connected with the head end of motor 41), land 37 uncovers port 52 and the right side of chamber 56 is connected with the pump -14 through inlet port 12, passage 25, annular chamber 23, plunger groove 47, port 62, conduit 61 and fitting 59. The fluid delivered to chamber 56 escapes to sump 15 through the clearance space 58 and exhaust manifold 29, but, since space 58 constitutes a restricted flow path, a back pressure is developed in chamber 56 that shifts seat 55 to the left into engagement with shoulder 57. This movement of seat 55 increases the bias that spring 53 exerts on valve 52 and thus, increases its cracking pressure and the maximum system pressure established by relief valve 51. Therefore, when motor 41 is movingin the rod end-contracting direction the system supplies a higher operating pressure than when the motor 41 is moving in the opposite direction or when motor 44 is moving in either of its two directions of motion.

When valve plunger 18 is moved from its extreme left hand position, port 62 will be covered by land 37 and the supply of fluid to chamber 56 will be interrupted. The fluid trapped in the conduit 61, fitting and the right side of chamber 56 escapes to sump 15 through the restricted clearance 58, thereby dissipating the pressure in chamber 56. Seat 55 now moves to the right under the action of spring 53. When seat 55 reaches the illustrated position, the preload in spring 53 will have reduced to the initial lower value.

Although the preferred embodiment of the invention uses only one port d2 in bore 16, and thus supplies fluid at the higher operating pressure only to the head end of motor 41, it will be obvious that a second port 62 can be provided in the fixed land between chambers 22' and 23. This second port 62 also would be connected with the right end of chamber 56 and, therefore, in this case the higher operating pressure would be supplied to both ends of motor 41. 7

It also will be apparent that the port or ports 62 can be formed in bore 17 so that the higher operating pressure is supplied to one or both sides of motor 44 rather than motor 42, and that each of the bores 16, 1'7 can be provided with one port 62 so that one end of each of the motors 41 and 4-4 receives the higher operating pressure. In the case where both sides of motor 44 are to receive the higher operating pressure, then, sine/e plunger 19 is downstream of plunger 18 in the series supply path, fluid can be supplied to chamber 56 through a single port 62 located in either passage 27 or passage 28.

As stated previously, the drawings and description relate only to the preferred form of the invention. Since changes, some of which have been mentioned, can be (a) a pump and a sump;

(b) at least two control valves connected with the pump, each valve having an outlet and first and second positions in which, respectively, the outlet is connected with and disconnected from the pump;

(0) a pressure relief valve connected with the pump and the sump;

(d) first means, including a fluid pressure motor, connected with the relief valve for varying its cracking pressure; and

(e) second means for pressurizing and venting the fluid pressure motor when one of the control valves is in one and the other of its first and second positions, respectively,

(f) the second means including a control port associated with said one control valve, a passage independent of the connection between the pump and the control valves and interconnecting the control port and the fluid pressure motor, and valve means carried by said one control valve and controlling flow through the control port.

2. A fluid system as defined in claim 1 (a) in which the second means also includes a restricted vent passage connecting the fluid pressure motor with the sump; and

(b) in which the valve means closes the control port when said one control valve is in its second position and connects the control port with the pump when said one control valve is in its first position.

3. In combination (a) a control valve including an inlet passage, an exhaust passage, a pair of outlet passages and a movable valve element having a first position in which one outlet passage is connected with the inlet passage and the other outlet passage is connected with the exhaust passage, and a second position in which the connections between the outlet passages and the inlet and exhaust passages are reversed;

(b) a relief valve subject to the pressure in the inlet passage and arranged to limit the pressure in that passage by by-passing fluid to the exhaust passage;

(0) means, including a fluid pressure motor, connected with the relief valve for varying its cracking pressure;

(0!) a control port associated with the movable valve element and arranged to be closed by that element when the latter is in its first position and to be connected with the inlet passage by that element when the latter is in its second position;

(e) passage means connecting the control port with the fluid pressure motor; and

(f) restricted passage means connecting the fluid pressure motor with the exhaust passage.

References Cited in the file of this patent UNITED STATES PATENTS 3,023,584 Markovich Mar. 6, 1962 

1. A FLUID SYSTEM COMPRISING (A) A PUMP AND A SUMP; (B) AT LEAST TWO CONTROL VALVES CONNECTED WITH THE PUMP, EACH VALVE HAVING AN OUTLET AND FIRST AND SECOND POSITIONS IN WHICH, RESPECTIVELY, THE OUTLET IS CONNECTED WITH AND DISCONNECTED FROM THE PUMP; (C) A PRESSURE RELIEF VALVE CONNECTED WITH THE PUMP AND THE SUMP; (D) FIRST MEANS, INCLUDING A FLUID PRESSURE MOTOR, CONNECTED WITH THE RELIEF VALVE FOR VARYING ITS CRACKING PRESSURE; AND (E) SECOND MEANS FOR PRESSURIZING AND VENTING THE FLUID PRESSURE MOTOR WHEN ONE OF THE CONTROL VALVES IS IN ONE AND THE OTHER OF ITS FIRST AND SECOND POSITIONS, RESPECTIVELY, (F) THE SECOND MEANS INCLUDING A CONTROL PORT ASSOCIATED WITH SAID ONE CONTROL VALVE, A PASSAGE INDEPENDENT OF THE CONNECTION BETWEEN THE PUMP AND THE CONTROL VALVES AND INTERCONNECTING THE CONTROL PORT AND THE FLUID PRESSURE MOTOR, AND VALVE MEANS CARRIED BY SAID ONE CONTROL VALVE AND CONTROLLING FLOW THROUGH THE CONTROL PORT. 